The year was 1990. It was the “Third Summer of Love”, the Happy Mondays were chanting, “It’s gotta be a loose fit”, and it looked as though high heels would never again be worn by anyone under 30. Fashion culture was changing, and the freckle-faced girl wearing a feather headdress, love beads and little else on the July cover of The Face magazine was on her way to becoming one of the world’s most photographed women. Years later, early images of Kate Moss, as taken by the photographer Corinne Day, would be sold for between £5000 and £10,000. A bargain, as it turns out. In July this year, when Christie’s announced it would be auctioning photographs of the British supermodel that included works by Irving Penn, Annie Leibovitz, Bruce Weber and Mario Sorrenti, the estimated price tag for the collection was £1,000,000.

Moss is often compared to those earlier blank slates for dreams and desires of the time, Marilyn Monroe and Greta Garbo. Seemingly capable of channelling any icon of any era, male or female, she recently appeared in UK Vogue as a sultry Brigitte Bardot, and has also “done” David Bowie. To complete the picture, she hangs out with icons and is particularly drawn to those, such as Marianne Faithfull and Anita Pallenberg, who barely survived the decadent rock lifestyle of the 1970s. Unlike her pals, Moss wears the slightly tarnished image of rockstar-girlfriend-model well, a one-woman jet set who always looks like she’s with the band.

In the 1990s, she was the anti-supermodel supermodel who ushered in the era of the waif. Twenty years ago, fashion was all about Christy, Linda, Naomi and Claudia – muscular, towering beauties, or “garment missiles”, as Vanity Fair writer AA Gill described them, strutting down the catwalk “like identical assassins”. Moss was an anomaly, a realistic, approachable ideal who brought “a degree of normality” to fashion’s impossible, synthetic standards and represented a new “type” that Charlotte Cotton, a British curator of photography, labelled “imperfect beauty”. It was a look that saw her modelling at every major fashion show, seamlessly crossing from grunge in New York to couture in Paris. Later, she would claim that she never walked the catwalk sober. Along the way she went from dating movie stars to drug addicts, checked in and out of rehab for “exhaustion”, had a baby and denied again and again that she was anorexic. In 2005, caught on grainy video snorting white powder from a plastic bag, she was dropped by all her major clients only to win most of them back within a season – and then some, increasing her annual earnings from £2.5 to £4 million. At the age of 32, she was at the height of her career and made a diet of vodka and cocaine look like a beauty regimen. It seemed being a hopeless role model might just be the secret of her success.

Though not the highest paid model of all time, she may well be the most popular, not least because she permanently changed what a fashion model could look like

Attempts to account for Moss’s appeal began early in her career. In Catwalk, the cult 1996 backstage documentary, the filmmaker prompts Moss to comment on whether she represents something, possibly a response to the Amazonian models of the 1980s. From underneath the hands of three hairdressers, she gazes up at him, blank and wide-eyed, finally responding: “What was the question?”

Moss has never been one to say much. She doesn’t give interviews, and friends and those close to her are notoriously tight-lipped. Allen Ginsberg once said of Bob Dylan, “I don’t know him because I don’t think there is any him. I don’t think he’s got a self.” That’s the problem with icons. For all the columns written about her, Moss remains an ideal, not a woman; she is all image.

John Hartley, the cultural critic, described this image as “a newsworthy bearer of ‘signs of the times’”, one that over 25 years has documented shifts in “taste, culture, lifestyle and experience”, as well as being an agent for change. This is, of course, what fashion does, a point not lost on the art world. Lucien Freud has painted Moss’s pregnant body, Sam Taylor-Wood photographed her as the Madonna, Banksy did her as a Warholesque “Marilyn”, Marc Quinn sculpted and contorted her as “a knotted Venus of our age” and, most recently, Chris Levine photographed her in 3-D. While artists can’t resist the temptation to capture her essence as something beyond herself, over on the seamier side of the image-making world, the demand for shots of the “real” Moss never fades. As paparazzo Darryn Lyons, the Australian founder of the London-based Big Pictures agency, once put it: “Kate Moss is always a story.”

But no one gets closer to the “truth” than the model herself. Launching a line of clothes she had designed in collaboration with Topshop, Moss posed in the window of the British clothing brand’s Oxford Circus store. She was cast not as the designer but as a living mannequin, surrounded by store dummies wearing the coined vests, fedoras, sequined T-shirts and cut-away dresses that would quickly become part of the global fashion landscape. The spectacle was a self-conscious act that confirmed what the thousands of queuing shoppers already knew: they were buying far more than clothes.

Moss has spent much of her life as a commodity. She was 14 when a model agent, Sarah Doukas, spotted her perched on a suitcase at JFK airport – a bored teenager with “God-given bone structure”. Now 39, she is at an age when few models expect to be working, yet her appeal is undiminished. She currently heads campaigns for Givenchy, Versace and Vivienne Westwood, as well as a raft of lesser known brands; she returned to the catwalk earlier this year for her friend Marc Jacobs; and in magazines her look remains compelling, making a $12 top seem essential and a $3770 swimsuit seem, well, plausible.

Though not the highest paid model of all time, she may well be the most popular, not least because she permanently changed what a fashion model could look like. She emerged at a time when a generation raised on the mix of fashion, music, art and subcultural style found in publications such as The Face was looking for something other than the high-octane consumerism that the supermodels represented. Corinne Day’s early shots of Moss were emblematic of a broader movement intent on injecting social and journalistic values into fashion imagery, or at least a sense of ordinariness more in line with young people’s lives.

Moss undoubtedly has what Vogue writer Hamish Bowles described as “preternatural elegance”, but she has always made clothes look lived in. It’s a talent that has only increased with age as she reveals an uncanny ability to impart the narrative of her lifestyle to a garment. For those who follow fashion closely, it’s this, more than the details of her lifestyle itself, that explains her appeal. In the current Vivienne Westwood campaign she wears a T-shirt loosely slung over an unravelling beaded dress, garments that look like they’ve been partying all night or pulled from the bedroom floor. Moss – gaunt and pale – looks hardly less crumpled. In the Givenchy campaign, the clothes couldn’t be more classic, but again Moss looks unpolished, wearing minimal make-up, her hair ungroomed. Of course, the gallery of Moss’s image is not without its glossy representations of airbrushed beauty, exotic locations and expensive clothes, but even then she looks like no one else. Other models come and go, ephemeral as the fashions they wear, but Moss remains, the ideal for an age, an imperfect beauty, still within reach.

Karen de Perthuis is a writer and fashion scholar. She teaches fashion and design at the University of Technology, Sydney, and the University of Western Sydney.

The year was 1990. It was the “Third Summer of Love”, the Happy Mondays were chanting, “It’s gotta be a loose fit”, and it looked as though high heels would never again be worn by anyone under 30. Fashion culture was changing, and the freckle-faced girl wearing a feather headdress, love beads and little else on the July cover of The Face magazine was on her way to becoming one of the world’s most photographed women. Years later, early images of Kate Moss, as taken by the photographer Corinne Day, would be sold for between £5000 and £10,000. A bargain, as it turns out. In July this year, when Christie’s announced it would be auctioning photographs of the British supermodel that included works by Irving Penn, Annie Leibovitz, Bruce Weber and Mario Sorrenti, the estimated price tag for the collection was £1,000,000....